go/printer: implement SourcePos mode
If a printer is configured with the SourcePos mode
set, it will emit //-line comments as necessary to
ensure that the result - if reparsed - reflects the
original source position information.
This change required a bit of reworking of the
output section in printer.go. Specifically:
- Introduced new Config mode 'SourcePos'.
- Introduced new position 'out' which tracks the
position of the generated output if it were read
in again. If there is a discrepancy between out
and the current AST/source position, a //line
comment is emitted to correct for it.
- Lazy emission of indentation so that //line
comments can be placed correctly. As a result,
the trimmer will have to do less work.
- Merged writeItem into writeString.
- Merged writeByteN into writeByte.
- Use a []byte instead of a byte.Buffer both in the
printer and in the trimmer (eliminates dependency).
Also: introduced explicit printer.Mode type (in
sync w/ parser.Mode, scanner.Mode, etc.)
Runs all tests. Applied gofmt to src, misc w/o changes.
Fixes #1047.
Fixes #2697.
R=rsc, rsc
CC=golang-dev
https://golang.org/cl/5643066
diff --git a/doc/go1.html b/doc/go1.html
index c864391..fce1c07 100644
--- a/doc/go1.html
+++ b/doc/go1.html
@@ -1050,6 +1050,15 @@
</p>
<p>
+A concrete <code>Mode</code> type was introduced for configuration mode flags
+in the packages
+<a href="/pkg/go/scanner/"><code>go/scanner</code></a>,
+<a href="/pkg/go/parser/"><code>go/parser</code></a>,
+<a href="/pkg/go/printer/"><code>go/printer</code></a>, and
+<a href="/pkg/go/doc/"><code>go/doc</code></a>.
+</p>
+
+<p>
The modes <code>AllowIllegalChars</code> and <code>InsertSemis</code> have been removed
from the <a href="/pkg/go/scanner/"><code>go/scanner</code></a> package. They were mostly
useful for scanning text other then Go source files. Instead, the
@@ -1076,6 +1085,17 @@
</p>
<p>
+The <a href="/pkg/go/printer/"><code>go/printer</code></a> package supports an additional
+configuration mode <a href="/pkg/go/printer/#Mode"><code>SourcePos</code></a>;
+if set, the printer will emit <code>//line</code> comments such that the generated
+output contains the original source code position information. The new type
+<a href="/pkg/go/printer/#CommentedNode"><code>CommentedNode</code></a> can be
+used to provide comments associated with an arbitrary
+<a href="/pkg/go/ast/#Node"><code>ast.Node</code></a> (until now only
+<a href="/pkg/go/ast/#File"><code>ast.File</code></a> carried comment information).
+</p>
+
+<p>
The type names of the <a href="/pkg/go/doc/"><code>go/doc</code></a> package have been
streamlined by removing the <code>Doc</code> suffix: <code>PackageDoc</code>
is now <code>Package</code>, <code>ValueDoc</code> is <code>Value</code>, etc.
diff --git a/doc/go1.tmpl b/doc/go1.tmpl
index f37f951..985cf97 100644
--- a/doc/go1.tmpl
+++ b/doc/go1.tmpl
@@ -953,6 +953,15 @@
</p>
<p>
+A concrete <code>Mode</code> type was introduced for configuration mode flags
+in the packages
+<a href="/pkg/go/scanner/"><code>go/scanner</code></a>,
+<a href="/pkg/go/parser/"><code>go/parser</code></a>,
+<a href="/pkg/go/printer/"><code>go/printer</code></a>, and
+<a href="/pkg/go/doc/"><code>go/doc</code></a>.
+</p>
+
+<p>
The modes <code>AllowIllegalChars</code> and <code>InsertSemis</code> have been removed
from the <a href="/pkg/go/scanner/"><code>go/scanner</code></a> package. They were mostly
useful for scanning text other then Go source files. Instead, the
@@ -979,6 +988,17 @@
</p>
<p>
+The <a href="/pkg/go/printer/"><code>go/printer</code></a> package supports an additional
+configuration mode <a href="/pkg/go/printer/#Mode"><code>SourcePos</code></a>;
+if set, the printer will emit <code>//line</code> comments such that the generated
+output contains the original source code position information. The new type
+<a href="/pkg/go/printer/#CommentedNode"><code>CommentedNode</code></a> can be
+used to provide comments associated with an arbitrary
+<a href="/pkg/go/ast/#Node"><code>ast.Node</code></a> (until now only
+<a href="/pkg/go/ast/#File"><code>ast.File</code></a> carried comment information).
+</p>
+
+<p>
The type names of the <a href="/pkg/go/doc/"><code>go/doc</code></a> package have been
streamlined by removing the <code>Doc</code> suffix: <code>PackageDoc</code>
is now <code>Package</code>, <code>ValueDoc</code> is <code>Value</code>, etc.
diff --git a/src/cmd/cgo/godefs.go b/src/cmd/cgo/godefs.go
index 6838729..478ed26 100644
--- a/src/cmd/cgo/godefs.go
+++ b/src/cmd/cgo/godefs.go
@@ -109,7 +109,7 @@
}
}
- printer.Fprint(&buf, fset, f.AST)
+ conf.Fprint(&buf, fset, f.AST)
return buf.String()
}
diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go
index 2c01074..bfbcf50 100644
--- a/src/cmd/cgo/out.go
+++ b/src/cmd/cgo/out.go
@@ -17,6 +17,8 @@
"strings"
)
+var conf = printer.Config{Mode: printer.SourcePos, Tabwidth: 8}
+
// writeDefs creates output files to be compiled by 6g, 6c, and gcc.
// (The comments here say 6g and 6c but the code applies to the 8 and 5 tools too.)
func (p *Package) writeDefs() {
@@ -57,7 +59,7 @@
for name, def := range typedef {
fmt.Fprintf(fgo2, "type %s ", name)
- printer.Fprint(fgo2, fset, def)
+ conf.Fprint(fgo2, fset, def)
fmt.Fprintf(fgo2, "\n\n")
}
fmt.Fprintf(fgo2, "type _Ctype_void [0]byte\n")
@@ -87,7 +89,7 @@
fmt.Fprintf(fc, "\n")
fmt.Fprintf(fgo2, "var %s ", n.Mangle)
- printer.Fprint(fgo2, fset, &ast.StarExpr{X: n.Type.Go})
+ conf.Fprint(fgo2, fset, &ast.StarExpr{X: n.Type.Go})
fmt.Fprintf(fgo2, "\n")
}
fmt.Fprintf(fc, "\n")
@@ -255,7 +257,7 @@
Name: ast.NewIdent(n.Mangle),
Type: gtype,
}
- printer.Fprint(fgo2, fset, d)
+ conf.Fprint(fgo2, fset, d)
if *gccgo {
fmt.Fprintf(fgo2, " __asm__(\"%s\")\n", n.C)
} else {
@@ -327,8 +329,7 @@
// Write Go output: Go input with rewrites of C.xxx to _C_xxx.
fmt.Fprintf(fgo1, "// Created by cgo - DO NOT EDIT\n\n")
- fmt.Fprintf(fgo1, "//line %s:1\n", srcfile)
- printer.Fprint(fgo1, fset, f.AST)
+ conf.Fprint(fgo1, fset, f.AST)
// While we process the vars and funcs, also write 6c and gcc output.
// Gcc output starts with the preamble.
@@ -542,11 +543,11 @@
// a Go wrapper function.
if fn.Recv != nil {
fmt.Fprintf(fgo2, "func %s(recv ", goname)
- printer.Fprint(fgo2, fset, fn.Recv.List[0].Type)
+ conf.Fprint(fgo2, fset, fn.Recv.List[0].Type)
forFieldList(fntype.Params,
func(i int, atype ast.Expr) {
fmt.Fprintf(fgo2, ", p%d ", i)
- printer.Fprint(fgo2, fset, atype)
+ conf.Fprint(fgo2, fset, atype)
})
fmt.Fprintf(fgo2, ")")
if gccResult != "void" {
@@ -556,7 +557,7 @@
if i > 0 {
fmt.Fprint(fgo2, ", ")
}
- printer.Fprint(fgo2, fset, atype)
+ conf.Fprint(fgo2, fset, atype)
})
fmt.Fprint(fgo2, ")")
}
diff --git a/src/cmd/gofmt/gofmt.go b/src/cmd/gofmt/gofmt.go
index 6d610ad..55c01be 100644
--- a/src/cmd/gofmt/gofmt.go
+++ b/src/cmd/gofmt/gofmt.go
@@ -45,7 +45,7 @@
exitCode = 0
rewrite func(*ast.File) *ast.File
parserMode parser.Mode
- printerMode uint
+ printerMode printer.Mode
)
func report(err error) {
diff --git a/src/pkg/go/printer/printer.go b/src/pkg/go/printer/printer.go
index fe99e67..e9ab5fd 100644
--- a/src/pkg/go/printer/printer.go
+++ b/src/pkg/go/printer/printer.go
@@ -6,7 +6,6 @@
package printer
import (
- "bytes"
"fmt"
"go/ast"
"go/token"
@@ -51,22 +50,22 @@
fset *token.FileSet
// Current state
- output bytes.Buffer // raw printer result
+ output []byte // raw printer result
indent int // current indentation
mode pmode // current printer mode
impliedSemi bool // if set, a linebreak implies a semicolon
lastTok token.Token // the last token printed (token.ILLEGAL if it's whitespace)
wsbuf []whiteSpace // delayed white space
- // The (possibly estimated) position in the generated output;
- // in AST space (i.e., pos is set whenever a token position is
- // known accurately, and updated dependending on what has been
- // written).
- pos token.Position
-
- // The value of pos immediately after the last item has been
- // written using writeItem.
- last token.Position
+ // Positions
+ // The out position differs from the pos position when the result
+ // formatting differs from the source formatting (in the amount of
+ // white space). If there's a difference and SourcePos is set in
+ // ConfigMode, //line comments are used in the output to restore
+ // original source positions for a reader.
+ pos token.Position // current position in AST (source) space
+ out token.Position // current position in output space
+ last token.Position // value of pos after calling writeString
// The list of all source comments, in order of appearance.
comments []*ast.CommentGroup // may be nil
@@ -89,6 +88,8 @@
func (p *printer) init(cfg *Config, fset *token.FileSet, nodeSizes map[ast.Node]int) {
p.Config = *cfg
p.fset = fset
+ p.pos = token.Position{Line: 1, Column: 1}
+ p.out = token.Position{Line: 1, Column: 1}
p.wsbuf = make([]whiteSpace, 0, 16) // whitespace sequences are short
p.nodeSizes = nodeSizes
p.cachedPos = -1
@@ -151,41 +152,57 @@
return p.cachedLine
}
-// writeByte writes ch to p.output and updates p.pos.
-func (p *printer) writeByte(ch byte) {
- p.output.WriteByte(ch)
- p.pos.Offset++
- p.pos.Column++
+// atLineBegin emits a //line comment if necessary and prints indentation.
+func (p *printer) atLineBegin(pos token.Position) {
+ // write a //line comment if necessary
+ if p.Config.Mode&SourcePos != 0 && pos.IsValid() && (p.out.Line != pos.Line || p.out.Filename != pos.Filename) {
+ p.output = append(p.output, tabwriter.Escape) // protect '\n' in //line from tabwriter interpretation
+ p.output = append(p.output, fmt.Sprintf("//line %s:%d\n", pos.Filename, pos.Line)...)
+ p.output = append(p.output, tabwriter.Escape)
+ // p.out must match the //line comment
+ p.out.Filename = pos.Filename
+ p.out.Line = pos.Line
+ }
+ // write indentation
+ // use "hard" htabs - indentation columns
+ // must not be discarded by the tabwriter
+ for i := 0; i < p.indent; i++ {
+ p.output = append(p.output, '\t')
+ }
+
+ // update positions
+ i := p.indent
+ p.pos.Offset += i
+ p.pos.Column += i
+ p.out.Column += i
+}
+
+// writeByte writes ch n times to p.output and updates p.pos.
+func (p *printer) writeByte(ch byte, n int) {
+ if p.out.Column == 1 {
+ p.atLineBegin(p.pos)
+ }
+
+ for i := 0; i < n; i++ {
+ p.output = append(p.output, ch)
+ }
+
+ // update positions
+ p.pos.Offset += n
if ch == '\n' || ch == '\f' {
- // write indentation
- // use "hard" htabs - indentation columns
- // must not be discarded by the tabwriter
- const htabs = "\t\t\t\t\t\t\t\t"
- j := p.indent
- for j > len(htabs) {
- p.output.WriteString(htabs)
- j -= len(htabs)
- }
- p.output.WriteString(htabs[0:j])
-
- // update p.pos
- p.pos.Line++
- p.pos.Offset += p.indent
- p.pos.Column = 1 + p.indent
+ p.pos.Line += n
+ p.out.Line += n
+ p.pos.Column = 1
+ p.out.Column = 1
+ return
}
+ p.pos.Column += n
+ p.out.Column += n
}
-// writeByteN writes ch n times to p.output and updates p.pos.
-func (p *printer) writeByteN(ch byte, n int) {
- for n > 0 {
- p.writeByte(ch)
- n--
- }
-}
-
-// writeString writes the string s to p.output and updates p.pos.
-// If isLit is set, s is escaped w/ tabwriter.Escape characters
+// writeString writes the string s to p.output and updates p.pos, p.out,
+// and p.last. If isLit is set, s is escaped w/ tabwriter.Escape characters
// to protect s from being interpreted by the tabwriter.
//
// Note: writeString is only used to write Go tokens, literals, and
@@ -195,59 +212,66 @@
// avoids processing extra escape characters and reduces run time of the
// printer benchmark by up to 10%.
//
-func (p *printer) writeString(s string, isLit bool) {
+func (p *printer) writeString(pos token.Position, s string, isLit bool) {
+ if p.out.Column == 1 {
+ p.atLineBegin(pos)
+ }
+
+ if pos.IsValid() {
+ // update p.pos (if pos is invalid, continue with existing p.pos)
+ // Note: Must do this after handling line beginnings because
+ // atLineBegin updates p.pos if there's indentation, but p.pos
+ // is the position of s.
+ p.pos = pos
+ // reset state if the file changed
+ // (used when printing merged ASTs of different files
+ // e.g., the result of ast.MergePackageFiles)
+ if p.last.IsValid() && p.last.Filename != pos.Filename {
+ p.indent = 0
+ p.mode = 0
+ p.wsbuf = p.wsbuf[0:0]
+ }
+ }
+
if isLit {
// Protect s such that is passes through the tabwriter
// unchanged. Note that valid Go programs cannot contain
// tabwriter.Escape bytes since they do not appear in legal
// UTF-8 sequences.
- p.output.WriteByte(tabwriter.Escape)
+ p.output = append(p.output, tabwriter.Escape)
}
- p.output.WriteString(s)
+ if debug {
+ p.output = append(p.output, fmt.Sprintf("/*%s*/", pos)...) // do not update p.pos!
+ }
+ p.output = append(p.output, s...)
- // update p.pos
+ // update positions
nlines := 0
- column := p.pos.Column + len(s)
+ var li int // index of last newline; valid if nlines > 0
for i := 0; i < len(s); i++ {
+ // Go tokens cannot contain '\f' - no need to look for it
if s[i] == '\n' {
nlines++
- column = len(s) - i
+ li = i
}
}
p.pos.Offset += len(s)
- p.pos.Line += nlines
- p.pos.Column = column
+ if nlines > 0 {
+ p.pos.Line += nlines
+ p.out.Line += nlines
+ c := len(s) - li
+ p.pos.Column = c
+ p.out.Column = c
+ } else {
+ p.pos.Column += len(s)
+ p.out.Column += len(s)
+ }
if isLit {
- p.output.WriteByte(tabwriter.Escape)
+ p.output = append(p.output, tabwriter.Escape)
}
-}
-// writeItem writes data at position pos. data is the text corresponding to
-// a single lexical token, but may also be comment text. pos is the actual
-// (or at least very accurately estimated) position of the data in the original
-// source text. writeItem updates p.last to the position immediately following
-// the data.
-//
-func (p *printer) writeItem(pos token.Position, data string, isLit bool) {
- if pos.IsValid() {
- // continue with previous position if we don't have a valid pos
- if p.last.IsValid() && p.last.Filename != pos.Filename {
- // the file has changed - reset state
- // (used when printing merged ASTs of different files
- // e.g., the result of ast.MergePackageFiles)
- p.indent = 0
- p.mode = 0
- p.wsbuf = p.wsbuf[0:0]
- }
- p.pos = pos
- }
- if debug {
- // do not update p.pos - use write0
- fmt.Fprintf(&p.output, "/*%s*/", pos)
- }
- p.writeString(data, isLit)
p.last = p.pos
}
@@ -262,14 +286,14 @@
// next item is a keyword.
//
func (p *printer) writeCommentPrefix(pos, next token.Position, prev, comment *ast.Comment, isKeyword bool) {
- if p.output.Len() == 0 {
+ if len(p.output) == 0 {
// the comment is the first item to be printed - don't write any whitespace
return
}
if pos.IsValid() && pos.Filename != p.last.Filename {
// comment in a different file - separate with newlines
- p.writeByteN('\f', maxNewlines)
+ p.writeByte('\f', maxNewlines)
return
}
@@ -309,7 +333,7 @@
// with a blank instead of a tab
sep = ' '
}
- p.writeByte(sep)
+ p.writeByte(sep, 1)
}
} else {
@@ -381,7 +405,7 @@
// use formfeeds to break columns before a comment;
// this is analogous to using formfeeds to separate
// individual lines of /*-style comments
- p.writeByteN('\f', nlimit(n))
+ p.writeByte('\f', nlimit(n))
p.indent = indent // restore indent
}
}
@@ -587,7 +611,7 @@
// shortcut common case of //-style comments
if text[1] == '/' {
- p.writeItem(p.posFor(comment.Pos()), text, true)
+ p.writeString(p.posFor(comment.Pos()), text, true)
return
}
@@ -601,11 +625,11 @@
pos := p.posFor(comment.Pos())
for i, line := range lines {
if i > 0 {
- p.writeByte('\f')
+ p.writeByte('\f', 1)
pos = p.pos
}
if len(line) > 0 {
- p.writeItem(pos, line, true)
+ p.writeString(pos, line, true)
}
}
}
@@ -643,7 +667,7 @@
// make sure we have a line break
if needsLinebreak {
- p.writeByte('\n')
+ p.writeByte('\n', 1)
wroteNewline = true
}
@@ -671,7 +695,7 @@
if last.Text[1] == '*' && p.lineFor(last.Pos()) == next.Line {
// the last comment is a /*-style comment and the next item
// follows on the same line: separate with an extra blank
- p.writeByte(' ')
+ p.writeByte(' ', 1)
}
// ensure that there is a line break after a //-style comment,
// before a closing '}' unless explicitly disabled, or at eof
@@ -722,7 +746,7 @@
}
fallthrough
default:
- p.writeByte(byte(ch))
+ p.writeByte(byte(ch), 1)
}
}
@@ -886,12 +910,12 @@
if droppedFF {
ch = '\f' // use formfeed since we dropped one before
}
- p.writeByteN(ch, n)
+ p.writeByte(ch, n)
impliedSemi = false
}
}
- p.writeItem(next, data, isLit)
+ p.writeString(next, data, isLit)
p.impliedSemi = impliedSemi
}
}
@@ -1027,7 +1051,7 @@
type trimmer struct {
output io.Writer
state int
- space bytes.Buffer
+ space []byte
}
// trimmer is implemented as a state machine.
@@ -1038,6 +1062,11 @@
inText // inside text
)
+func (p *trimmer) resetSpace() {
+ p.state = inSpace
+ p.space = p.space[0:0]
+}
+
// Design note: It is tempting to eliminate extra blanks occurring in
// whitespace in this function as it could simplify some
// of the blanks logic in the node printing functions.
@@ -1062,36 +1091,33 @@
case inSpace:
switch b {
case '\t', ' ':
- p.space.WriteByte(b) // WriteByte returns no errors
+ p.space = append(p.space, b)
case '\n', '\f':
- p.space.Reset() // discard trailing space
+ p.resetSpace() // discard trailing space
_, err = p.output.Write(aNewline)
case tabwriter.Escape:
- _, err = p.output.Write(p.space.Bytes())
+ _, err = p.output.Write(p.space)
p.state = inEscape
m = n + 1 // +1: skip tabwriter.Escape
default:
- _, err = p.output.Write(p.space.Bytes())
+ _, err = p.output.Write(p.space)
p.state = inText
m = n
}
case inEscape:
if b == tabwriter.Escape {
_, err = p.output.Write(data[m:n])
- p.state = inSpace
- p.space.Reset()
+ p.resetSpace()
}
case inText:
switch b {
case '\t', ' ':
_, err = p.output.Write(data[m:n])
- p.state = inSpace
- p.space.Reset()
- p.space.WriteByte(b) // WriteByte returns no errors
+ p.resetSpace()
+ p.space = append(p.space, b)
case '\n', '\f':
_, err = p.output.Write(data[m:n])
- p.state = inSpace
- p.space.Reset()
+ p.resetSpace()
_, err = p.output.Write(aNewline)
case tabwriter.Escape:
_, err = p.output.Write(data[m:n])
@@ -1110,8 +1136,7 @@
switch p.state {
case inEscape, inText:
_, err = p.output.Write(data[m:n])
- p.state = inSpace
- p.space.Reset()
+ p.resetSpace()
}
return
@@ -1120,16 +1145,19 @@
// ----------------------------------------------------------------------------
// Public interface
-// General printing is controlled with these Config.Mode flags.
+// A Mode value is a set of flags (or 0). They coontrol printing.
+type Mode uint
+
const (
- RawFormat uint = 1 << iota // do not use a tabwriter; if set, UseSpaces is ignored
+ RawFormat Mode = 1 << iota // do not use a tabwriter; if set, UseSpaces is ignored
TabIndent // use tabs for indentation independent of UseSpaces
UseSpaces // use spaces instead of tabs for alignment
+ SourcePos // emit //line comments to preserve original source positions
)
// A Config node controls the output of Fprint.
type Config struct {
- Mode uint // default: 0
+ Mode Mode // default: 0
Tabwidth int // default: 8
}
@@ -1170,7 +1198,7 @@
}
// write printer result via tabwriter/trimmer to output
- if _, err = output.Write(p.output.Bytes()); err != nil {
+ if _, err = output.Write(p.output); err != nil {
return
}
diff --git a/src/pkg/go/printer/printer_test.go b/src/pkg/go/printer/printer_test.go
index 9adf48c..a057881 100644
--- a/src/pkg/go/printer/printer_test.go
+++ b/src/pkg/go/printer/printer_test.go
@@ -223,7 +223,8 @@
}
}
-// Print and parse f with
+// testComment verifies that f can be parsed again after printing it
+// with its first comment set to comment at any possible source offset.
func testComment(t *testing.T, f *ast.File, srclen int, comment *ast.Comment) {
f.Comments[0].List[0] = comment
var buf bytes.Buffer
@@ -280,3 +281,128 @@
testComment(t, f, len(src), &ast.Comment{pos, "/*-style \n comment */"})
testComment(t, f, len(src), &ast.Comment{pos, "/*-style comment \n\n\n */"})
}
+
+type visitor chan *ast.Ident
+
+func (v visitor) Visit(n ast.Node) (w ast.Visitor) {
+ if ident, ok := n.(*ast.Ident); ok {
+ v <- ident
+ }
+ return v
+}
+
+// idents is an iterator that returns all idents in f via the result channel.
+func idents(f *ast.File) <-chan *ast.Ident {
+ v := make(visitor)
+ go func() {
+ ast.Walk(v, f)
+ close(v)
+ }()
+ return v
+}
+
+// identCount returns the number of identifiers found in f.
+func identCount(f *ast.File) int {
+ n := 0
+ for _ = range idents(f) {
+ n++
+ }
+ return n
+}
+
+// Verify that the SourcePos mode emits correct //line comments
+// by testing that position information for matching identifiers
+// is maintained.
+func TestSourcePos(t *testing.T) {
+ const src = `
+package p
+import ( "go/printer"; "math" )
+const pi = 3.14; var x = 0
+type t struct{ x, y, z int; u, v, w float32 }
+func (t *t) foo(a, b, c int) int {
+ return a*t.x + b*t.y +
+ // two extra lines here
+ // ...
+ c*t.z
+}
+`
+
+ // parse original
+ f1, err := parser.ParseFile(fset, "src", src, parser.ParseComments)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ // pretty-print original
+ var buf bytes.Buffer
+ err = (&Config{Mode: UseSpaces | SourcePos, Tabwidth: 8}).Fprint(&buf, fset, f1)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ // parse pretty printed original
+ // (//line comments must be interpreted even w/o parser.ParseComments set)
+ f2, err := parser.ParseFile(fset, "", buf.Bytes(), 0)
+ if err != nil {
+ t.Fatalf("%s\n%s", err, buf.Bytes())
+ }
+
+ // At this point the position information of identifiers in f2 should
+ // match the position information of corresponding identifiers in f1.
+
+ // number of identifiers must be > 0 (test should run) and must match
+ n1 := identCount(f1)
+ n2 := identCount(f2)
+ if n1 == 0 {
+ t.Fatal("got no idents")
+ }
+ if n2 != n1 {
+ t.Errorf("got %d idents; want %d", n2, n1)
+ }
+
+ // verify that all identifiers have correct line information
+ i2range := idents(f2)
+ for i1 := range idents(f1) {
+ i2 := <-i2range
+
+ if i2.Name != i1.Name {
+ t.Errorf("got ident %s; want %s", i2.Name, i1.Name)
+ }
+
+ l1 := fset.Position(i1.Pos()).Line
+ l2 := fset.Position(i2.Pos()).Line
+ if l2 != l1 {
+ t.Errorf("got line %d; want %d for %s", l2, l1, i1.Name)
+ }
+ }
+
+ if t.Failed() {
+ t.Logf("\n%s", buf.Bytes())
+ }
+}
+
+// TextX is a skeleton test that can be filled in for debugging one-off cases.
+// Do not remove.
+func TestX(t *testing.T) {
+ const src = `
+package p
+func _() {}
+`
+ // parse original
+ f, err := parser.ParseFile(fset, "src", src, parser.ParseComments)
+ if err != nil {
+ t.Fatal(err)
+ }
+
+ // pretty-print original
+ var buf bytes.Buffer
+ if err = (&Config{Mode: UseSpaces, Tabwidth: 8}).Fprint(&buf, fset, f); err != nil {
+ t.Fatal(err)
+ }
+
+ // parse pretty printed original
+ if _, err := parser.ParseFile(fset, "", buf.Bytes(), 0); err != nil {
+ t.Fatalf("%s\n%s", err, buf.Bytes())
+ }
+
+}
